Acid-induced amino side-chain interactions and secondary structure of solid poly-L-lysine probed by 15N and 13C solid state NMR and ab initio model calculations.
Acid-induced amino side-chain interactions and secondary structure of solid poly-L-lysine probed by 15N and 13C solid state NMR and ab initio model calculations.
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通过 15N 和 13C 固态 NMR 和从头算模型计算探测酸诱导的氨基侧链相互作用和固体聚 L-赖氨酸的二级结构。
DOI：
10.1021/ja901082a
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发表时间：
2009
影响因子：
15
通讯作者：
H. Limbach
中科院分区：
文献类型：
--
作者：
Alexandra Dos;Volkmar Schimming;Monique Chan Huot;H. Limbach
用高分辨固体(15)N和(13)C CPMAS核磁共振谱研究了干固体聚L赖氨酸的(15)N标记侧链氨基的酸碱和碱碱相互作用及其对二级结构的影响。在以前的研究中，我们已经证明，当酸碱比为1/氨基时，卤素酸HI、HCl和HBr在β-折叠结构中形成PLL盐，而在α-螺旋结构中不形成PLL盐，而HF和各种含氧酸在这两个二级结构中形成1：1的酸碱氢键络合物。在本研究中，我们在降低酸碱比的情况下进行了核磁共振实验，以阐明在这些条件下是否也形成了1：2和1：3的酸碱络合物。通常，含有HF、HBr、HCl、HI、CH(3)COOH、H(3)PO(4)、H(2)SO(4)或HNO(3)的PLL样品是在不同的pH下通过冷冻干燥得到的。作为比较，样品也是通过让干燥的无酸PLL与气体HCl相互作用而获得的。在理论部分，我们首先研究了不同酸碱络合物形成的可能性作为酸碱比和络合物形成的平衡常数的函数。利用这些信息，分析和指认了酸掺杂PLL的~(15)N核磁共振谱。事实上，可以获得在较低酸碱比下形成1：2和1：3酸碱复合体的证据。此外，在酸碱比约为0.8的情况下，PLL卤化物的盐结构已经被破坏。相反，当无酸的多L赖氨酸暴露在盐酸气体中时，氨基到氨基的双指数转化没有形成1：2和1：3的络合物。(13)CNMR表明，无酸PLL的β-折叠片状环境与盐酸反应迅速，而α-螺旋必须首先在缓慢的反应中转化为β-折叠片状，然后才能反应。有趣的是，在部分HCl掺杂后，暴露在气态H(2O)O中催化氨基和氨基相互转化为1：1、1：2和1：3的混合物。最后，对甲胺-酸模型络合物进行了密度泛函理论计算，辅助了~(15)N核磁共振的归属。
The acid-base and base-base interactions of the (15)N-labeled side-chain amino groups of dry solid poly-L-lysine (PLL) and the consequences for the secondary structure have been studied using high-resolution solid state (15)N and (13)C CPMAS NMR spectroscopy. In a previous study we had shown that at acid/base ratios of 1 per amino group the halogen acids HI, HCl and HBr form PLL salts in the beta-pleated sheet but not in the alpha-helical structure, whereas HF and various oxygen acids form 1:1 acid-base hydrogen-bonded complexes in both secondary structures. In the present study we performed NMR experiments at reduced acid/base ratios in order to elucidate whether also 1:2 and 1:3 acid-base complexes are formed under these conditions. Generally, the PLL samples containing HF, HBr, HCl, HI, CH(3)COOH, H(3)PO(4), H(2)SO(4), or HNO(3) were obtained by lyophilization at different pH. For comparison, samples were also obtained by letting dry acid-free PLL interact with gaseous HCl. In a theoretical section we first study the probability of the different acid-base complexes as a function of the acid/base ratio and the equilibrium constants of the complex formation. Using this information, the (15)N NMR spectra of acid doped PLL obtained were analyzed and assigned. Indeed, evidence for the formation of 1:2 and 1:3 acid-base complexes at lower acid/base ratios could be obtained. Moreover, the salt structures of the halides of PLL are already destroyed at acid/base ratios of about 0.8. By contrast, when acid-free poly-L-lysine is exposed to HCl gas, a biexponential conversion of amino groups into ammonium groups is observed without formation of 1:2 and 1:3 complexes. (13)C NMR reveals that the beta-pleated sheet environments of acid-free PLL react rapidly with HCl, whereas the alpha-helices first have to be converted in a slow reaction to beta-pleated sheets before they can react. Interestingly, after partial doping with HCl, exposure to gaseous H(2)O catalyzes the interconversion of the ammonium and amino groups into a mixture of 1:1, 1:2 and 1:3 complexes. Finally, the (15)N NMR assignments were assisted by DFT calculations on methylamine-acid model complexes.
极性溶液中 5-磷酸吡哆醛模型体系中耦合低和高势垒氢键的 NMR 研究
影响因子：
15
作者：
S. Sharif;G. S. Denisov;M. D. Toney;H. H. Limbach
通讯作者：
H. H. Limbach
质子与脂肪族叔二胺的螯合。
影响因子：
15
作者：
Yaghmaei,Sepideh;Khodagholian,Sevana;Kaiser,JMichael;Tham,FookS;Mueller,LeonardJ;Morton,ThomasHellman
通讯作者：
Morton,ThomasHellman